John Tefft

Date of Award

8-2007

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Chemical Engineering

Advisor

Douglas W. Bousfield

Second Committee Member

David J. Neivandt

Third Committee Member

Joseph M. Genco

Abstract

In the production of paper products, a fluid is often applied onto the paper surface. The depth of penetration of this fluid into the paper fiber network influences the final properties of the product. In the case of printing, ink pigment and ink vehicle (the oils that carry the pigment) interaction with the coating needs to be understood in the ever changing paper industry to create the best paper. The previous methods employed to describe the interaction of coatings was the Scanning Electron Microscope (SEM) but it was very time consuming. The Confocal Laser Scanning Microscope (CLSM) was found to give similar results with a lot less preparation time and sampling time. The CLSM was found to be able to give quantitative results of ink pigments location as well as ink vehicle movements in a greatly reduced timeframe. Confocal microscopes utilize a pinhole aperture to allow only in focus images to the photo detectors resulting in 1 um resolution in the xyz dimension. The light that is detected is generated by the lasers ability to excite fluorescent molecules like Rhodamine B that was used in the experiments or natural fluorophores like magenta pigment. The gain level is then used to determine the brightness of the resulting image. Coated sheets were stained with Rhodamine B dye and then measured using the CLSM to determine coating thickness. The samples were also printed with magenta and cyan/Rhodamine B mixed inks to characterize ink pigment and ink vehicle interactions. Barrier coating and samples with pits were also characterized using the CLSM to compare with known results. The gain levels used was determined to play a large affect on CLSM coating thickness measurements when compared with SEM coating thickness. CLSM and SEM data was also compared to mercury porosimetry taken of the samples but assumptions of coating pigment density as well as coating uniformity made caused the data to not correlate with the excepted means of measuring. Offset printing blanket roughness calculated from CLSM was compared to stylus profiler data to test reflected light roughness.

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